基于K均值聚类和开闭交替滤波的黄瓜叶片水滴荧光图像分割

为了监测温室黄瓜叶片湿润情况以计算叶片湿润时间并用于病害预警,利用K-均值聚类算法实现黄瓜叶片的水滴荧光图像分割。选择人工气候室培育的健康且洁净的黄瓜叶片作为试验试材,采用移液枪向叶面、叶缘部位上滴水,模拟不同的叶片湿润情形,使用荧光成像仪蓝光镜头在白天（07：00）和夜晚（18：00）分别采集图像。应用 K-均值聚类算法在L*a*b颜色空间对水滴图像进行分割,首先要将原始图像由RGB颜色空间转换到L*a*b颜色空间,然后在在L*a*b颜色空间中利用a*b*二维数据空间的颜色差异,以欧式距离度量像素间的相似度,使用K均值对图像进行聚类,聚类得到的图像灰度化后进一步用数学形态学中的开闭交替滤波方法进行校正,最终完成图像分割。利用该方法对10幅含有不同水滴数量的黄瓜叶片荧光图像进行分割,为了验证该方法的有效性,分别采用基于H分量直方图分割算法、主动轮廓即C_V模型分割方法、融合K均值聚类和Ncut算法作对比试验。试验结果表明,该方法的平均匹配率、误分率相较于其他3种方法有明显的优势,平均匹配率为81.27%、平均误分率为9.57%,较之于其他3种方法,平均匹配率分别提高了44.11、11.50、10.90百分点,平均误分率分别降低了23.03、5.47和5.05百分点。该方法能够较为准确地将水滴从图像中分割出来,这为用计算机器视觉的方法监测黄瓜叶片的润湿时间提供了新的思路。     

Post‐fire forestry management and nutrient losses in eucalyptus and pine plantations,Northern Portugal

The impact of different logging techniques on nutrient losses in burnt eucalyptus and pine forests in northern Portugal was investigated. A variety of logging techniques is used in the region resulting in varying amounts of slash debris on the slopes. The efficacy of this litter in reducing soil erosion is well established but less is known about the impact on nutrient losses. Small bounded plots were used to examine the impact of varying amounts of slash debris and pine‐needle cover on nutrient losses in overland flow and adsorbed to eroded sediment over 19 months during the first two–three years after fire. Nutrient losses in solution and adsorbed to eroded sediment were substantially higher on burnt terrain due to increased erosion and overland flow generation and high nutrient concentrations at the soil surface in the burned forests. Post‐fire logging techniques in eucalyptus forests resulting in large amounts of litter debris on the slopes are effective at reducing eroded sediment nutrient losses but less effective at reducing losses in solution. In pine forests, litter is largely ineffective in reducing solute and sediment nutrient losses. However, a covering of pine needles was shown to be highly effective in reducing eroded sediment nutrient losses and to a lesser extent solute losses. Conservational methods of logging are suggested for both eucalyptus and pine forests in the region. In the absence of such measures, the sustainability of short‐rotation eucalyptus forestry is questioned in northern Portugal. Copyright © 2000 John Wiley & Sons, Ltd.     

季节性冻融对色季拉森林土壤团聚体稳定性的影响

为分析季节性冻融对土壤团聚体稳定性的影响,以藏东南色季拉山森林土壤为研究对象,通过野外控制性试验利用湿筛法测定团聚体组成,分析了0—10 cm, 10—20 cm, 20—30 cm深度土层各粒径团粒结构变化,以及土壤含水量(SWC),0.25 mm水稳性团聚体含量(WSA)、平均质量直径(MWD)、平均几何直径(GMD)、分形维数D、可蚀性K值各指标之间的关系。结果表明：(1)季节性冻融导致大团粒含量减少,小团粒含量增加,土壤结构失调。(2)含水量是影响团聚体稳定性的重要因素之一。(3)季节性冻融作用整体上导致MWD,GMD变小,D值与K值变大,降低了土壤团聚体稳定性。(4)当土壤冻融次数在一定范围内STF-One中,WSA有所增加,土壤稳定性有所增强。(5)土壤团聚体WSA,MWD和GMD均与D值和K值呈负相关。(6)在SFT-Ys类型土壤中土壤结构变化,0.5 mm粒级是重要临界点。综上,研究为季节性冻融对土壤稳定性的影响提供数据支持,为冻土潜在受侵蚀情况提供理论依据。     

Soil sodicity as a result of periodical drought

Soil sodicity development is a process that depends nonlinearly on both salt concentration and composition of soil water. In particular in hot climates, soil water composition is subject to temporal variation due to dry–wet cycles. To investigate the effect of such cycles on soil salinity and sodicity, a simple root zone model is developed that accounts for annual salt accumulation and leaching periods. Cation exchange is simplified to considering only Ca/Na exchange, using the Gapon exchange equation. The resulting salt and Ca/Na-balances are solved for a series of dry/wet cycles with a standard numerical approach. Due to the nonlinearities in the Gapon equation, the fluctuations of soil salinity that may be induced, e.g. by fluctuating soil water content, affect sodicity development. Even for the case that salinity is in a periodic steady state, where salt concentrations do not increase on the long term, sodicity may still grow as a function of time from year to year. For the longer term, sodicity, as quantified by Exchangeable Sodium Percentage (ESP), approaches a maximum value that depends on drought and inflowing water quality, but not on soil cation exchange capacity. Analytical approaches for the salinity and sodicity developing under such fluctuating regimes appear to be in good agreement with numerical approximations and are very useful for checking numerical results and anticipating changes in practical situations.     

降雨量对洱海流域稻季氮磷湿沉降通量及浓度的影响

为了探究洱海流域稻季氮磷湿沉降规律,于2016及2017年稻季在大理洱海流域收集湿沉降样品,分析样品中总磷(total phosphorus,TP)、总氮(total nitrogen,TN)、NO_3~--N、NH_4~+-N等指标及其变化规律。结果表明,TN、TP湿沉降通量主要受降雨量支配,2016与2017年稻季单次降水TN、TP湿沉降通量与降雨量均呈极显著的线性正相关关系。TN、TP湿沉降浓度总体上随降雨量的增大而减小,同时与是否发生连续降雨及是否大规模施肥有关。以2017稻季氮素湿沉降为例,2017年稻季NH_4~+-N和NO_3~--N湿沉降对TN的占比分别为53.1%和20.6%,湿沉降以NH_4~+-N为主。可溶性无机氮(dissolved inorganic nitrogen,DIN)对TN的占比随着降雨量的增大而减小,随着连续降雨的延续而增大。2016及2017年稻季湿沉降TN质量浓度分别为0.87~4.03和0.90~6.85 mg/L,均远大于湖泊富营养化阀值,对洱海水生生态系统产生不利影响。     

多因素下全射流喷头射程计算模型及试验

为了深入研究多因素条件下全射流喷头射程公式,预测全射流喷头射程模型.采用组合法对全射流喷头射程进行试验设计,包括测量喷嘴直径、喷头仰角、工作压力、安装高度等因素,总结全射流喷头射程在不同因素下的变化规律,利用1stOpt软件进行数据分析得到全射流喷头射程计算公式,并利用此公式与当前常用的2个喷头射程公式进行对比分析.结果表明:随着工作压力的变化射程出现较大的变化,喷头射程随喷头仰角的增大呈先增大后减小的抛物线型变化,喷头安装高度对射程的影响较小,喷嘴直径越大喷头射程越大.全射流喷头射程与单个因素之间的关系与所建立的模型拟合较好,呈幂函数关系,计算射程与试验射程相差小于8%,研究结果可为全射流喷头射程的预测提供理论依据.     

Effects of Cooking on Anthocyanin Concentration and Bioactive Antioxidant Capacity in Glutinous and Non-Glutinous Purple Rice

Purple rice is a source of bioactive antioxidants for rice consumers. Loss of the major antioxidant compounds after a range of cooking processes was evaluated by measuring the changes in anthocyanin concentration (ATC) and antioxidant capacity (DPPH activity) of four non-glutinous and four glutinous genotypes. However, soaking in water prior to cooking generally decreased more ATC and antioxidant capacity in non-glutinous than in glutinous genotypes. Wet cooking (WC) and soaking before wet cooking (S-WC) led to lose almost all the ATC and antioxidant capacity with only slight variation between genotypes. In the glutinous genotype Pieisu, which had the highest raw rice ATC, ATC remained the highest when cooked by the WC method. By contrast, almost no ATC remained after WC and S-WC in the low ATC genotypes such as Kum Doi Saket. Overall, the loss of ATC was greater in non-glutinous than in glutinous genotypes for both WC and S-WC methods, but the reverse occurred for antioxidant capacity. WC using electric rice cooker retained higher ATC than the pressure cooking. Thus, for genotypes with high ATC and antioxidant capacity, the selection of cooking method is critical for retaining and stabilizing rice quality.     

典型森林树种对大气颗粒物湿沉降的影响

选择典型森林树种油松和侧柏作为研究对象,通过在2种树的冠层不同高度处(8,6,4,2m)布设湿沉降监测装置进行定位监测,比较单位叶面积滞尘量和降水对叶表面颗粒物冲刷率来分析2种树种对于大气颗粒物湿沉降的影响,并分析了树冠层不同高度颗粒物湿沉降以及不同粒径颗粒物湿沉降通量的变化规律,最后通过叶片显微结构来分析2种树种滞尘差异的原因。结果表明:(1)油松单位叶面积的滞尘量高于栓皮栎;降雨对2种树种叶面上大气颗粒物的冲刷率表现为栓皮栎高于油松。(2)油松枝下高2m处滞尘能力最强,大气颗粒物湿沉降通量最小;栓皮栎树冠中部4m处滞尘能力最强,且湿沉降通量最小。(3)油松冠层下部对于10~100μm污染物具有明显的截留作用,而栓皮栎的树冠上部对其具有更明显的截留作用。对于0.4~3μm和3~10μm颗粒物,油松的截留能力要强于栓皮栎。(4)油松和栓皮栎在叶表面显微结构的差异导致两者吸附颗粒物能力不同,油松叶片具有更多的褶皱、开度和密度较高的气孔以及相对较深的沟槽使其具有更强的吸附颗粒物的能力。     

2006—2015年中国小麦质量年度变化

【目的】中国小麦由强筋小麦、中强筋小麦、中筋小麦和弱筋小麦4种类型构成,分析近10年来各类型小麦年度质量变化,探讨小麦生产质量现状、存在的问题和解决方法,为小麦生产、科研、购销和加工等环节提供必要的参考。【方法】对2006—2015年中国小麦生产区742个小麦品种7 561份样品的容重、蛋白质含量、湿面筋含量、沉淀指数和面团流变学特性进行测定,分析各类型小麦年度比例和8个主要品质性状年度变化。【结果】小麦品种结构有所改善,但达标样品比例较低。从品种比例看,强筋品种、中强筋品种、中筋品种和弱筋品种比例分别为12.6%、16.7%、68.7%和2.0%,年度间保持稳定。从样品比例看,强筋小麦、中强筋小麦、中筋小麦和弱筋小麦样品比例分别为21.0%、16.9%、49.4%和3.8%;各类型小麦样品比例年度间变化差异较大,年度间强筋小麦和中筋小麦呈此消彼长趋势,中强筋小麦呈缓慢增加趋势,弱筋小麦呈下降趋势。从达标样品比例看,各类型小麦达标比例较低,强筋小麦、中强筋小麦、中筋小麦和弱筋小麦达标比例分别为4.8%、4.6%、25.0%和0.4%。中国小麦总体质量表现为中筋小麦水平,容重、蛋白质含量和湿面筋含量年度间变化趋势不明显,沉淀指数、粉质和拉伸参数呈小幅下降趋势。强筋小麦、中强筋小麦和中筋小麦品质性状年度间保持相对稳定,沉淀指数、粉质和拉伸参数变化趋势基本相同;弱筋小麦近年来蛋白质含量、湿面筋含量和沉淀指数年度平均值增加,品质下降。不同类型小麦品质性状差异较大,容重年度平均值大小依次为中强筋小麦强筋小麦中筋小麦弱筋小麦,蛋白质含量和湿面筋含量年度平均值大小依次为强筋小麦中筋小麦中强筋小麦弱筋小麦,沉淀指数、粉质和拉伸参数年度平均值大小依次为强筋小麦中强筋小麦中筋小麦、弱筋小麦;年度平均值变幅不同,其中沉淀指数、粉质和拉伸参数年度平均值变幅大小依次为强筋小麦中强筋小麦中筋小麦、弱筋小麦。【结论】中国小麦品种结构有所改善,各类型小麦达标比例较低,小麦质量有较大提升空间。应通过选育和推广高产优质专用小麦品种、合理增加现有各类型优质小麦品种面积和加大政策扶持力度等途径,优化品种结构,提高小麦质量。     

一种湍流计算的非线性PANS模型

大多数雷诺平均湍流模型(RANS)基于线性和各项同性假设求解雷诺应力(Reynolds stress),因此对高压力梯度区、大曲率回流以及复杂的分离流动的预测误差较大.在近壁区较少网格的条件下,部分时均(PANS)方法被认为比大涡模拟(LES)获得结果更好.通过RNG k-ε湍流模型构造部分时均化模型,引入雷诺应力的非线性求解方法,提出了一种新的非线性PANS模型,并应用该非线性PANS模型分别对绕NACA0015水翼翼型流场和90°长方形截面弯管内流场进行了流动的数值模拟.结果表明:非线性PANS模型的数值结果与试验数据吻合较好,其在高压力梯度区的预测准确性高,并能准确预测流动分离诱发的三维非线性流动,证明了该方法捕捉高压力梯度、大曲率流动的有效性.该计算方法可以用来预测透平机械内部复杂的涡结构.